This invention relates to a method for forming tiles of ceramic material, and in 5 particular tiles having dimensions exceeding 50xc3x9750 cm.
Methods for forming small-dimension ceramic tiles, i.e. having maximum dimensions of 40xc3x9740 cm, are known; these comprise preparing a mass of powders, precompacting it to obtain a flat blank, depositing on said blank, in a controlled manner, at least a second layer of powders to form a surface decoration, and finally pressing the decorated blank to obtain the formed tile.
All the known methods, which involve a material precompacting stage, solve the problem of deaerating the powder mass, however the percentage reduction in the thickness of the powder mass during material precompacting is insufficient to ensure surface stability of the precompacted blank.
As a result, although the powders of said at least one second layer for forming the tile surface decoration are intimately bonded to the powders of the upper surface of the blank, they do not rest on a stable surface, with the consequence that mixing of the decoration powders occurs during transportation of the slab to the second pressing stage. Particularly in the case of elaborately decorated tiles, this causes decoration defects in the finished tile, which show mainly as lack of sharpness along the decoration edges.
An object of the present invention is to solve the problems of the known art within the framework of a simple and rational solution.
A further object of the invention is to form large-dimension tiles, i.e. tiles having a size up to 180xc3x97120 cm and beyond.
The invention attains said objects by virtue of the characteristics stated in the claims.
In particular, with the method of the invention the precompacting pressure is sufficient to create a consistent powder slab presenting good surface stability while at the same time allowing the powders of said at least second layer to mix intimately with the powders of the surface layer of the slab. This ensures that during transport of the decorated slab and its subsequent pressing there is no movement of the decoration powders relative to the surface of the precompacted slab, to consequently obtain a perfect sharpness of the decoration edges.
The invention also provides a forming plant, the special characteristics of which are defined in the claims.
To better clarify the method of the invention and the relative plant, a preferred embodiment thereof is described hereinafter by way of non-limiting example and is illustrated in the accompanying drawings.